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A 25.9MW hybrid solar-diesel system is to be delivered by Aggreko to power a new Gold Fields greenfield gold and silver mine high in the Chilean Andes. Jonathan Spencer Jones investigates.
The system is to be comprised of 9.9MW of solar PV and 16MW of thermal diesel gensets to provide a total of 25.9MW to fully power the new Salares Norte open pit mine at an altitude of 4,500m in the Andes in northern Chile's Atacama region.
The location is remote – 190km from the nearest town – and the weather conditions are extreme, with snow and high winds commonly experienced.
The solution, two years in the making, is designed to meet the rigours of the location. The Aggreko modified high altitude performance diesel gensets provide back up to the solar and incorporate spinning reserve and cold reserve units to manage peaks in demand.
Such peaks generally occur when starting up the crushing engines or crushing larger ore masses, otherwise the demand is fairly constant throughout day and night.
"We worked hard to develop the best solution for the mine with the main requirements being reliability due to the remoteness and efficient and environmentally friendly," Pablo Varela, Aggreko's Latin America Managing Director, told Power Engineering International in an exclusive interview.
He says that several options were investigated but the altitude was the limiting factor. For example, aside from the current high costs of storage, the current battery technologies cannot be incorporated due to the impact of the atmospheric pressure on the inverters.
Diesel is then the next natural option, offering benefits such as being easy to manage and more efficient than other thermal solutions.
"The solution meets and surpasses the Chilean government's environmental standards, which are among the strictest in Latin America, as well as Gold Fields' requirement of a minimum 20% renewable power generation for its mining operations," he says.
Another complexity Varela mentions is the mountainous topography of the site, which presented an engineering design challenge. This, along with the site use restrictions set by government, will result in the solar arrays being distributed in three "crazy shaped" locations, the main site with about 14MW and the two smaller sites making up the balance.
Moreover, ongoing cleaning and maintenance will be required to keep the solar panels free of wind-driven sand and snow to prevent mechanical overload and to maintain their operational efficiency.
The system will be Aggreko's largest solar PV installation in Latin America. Once complete, it is expected to achieve $7.4 million in cost of energy savings over the next decade and a further $1.1 million in carbon tax offset in addition to 104,000 tonnes of carbon emissions savings.
Along with the design, another novel aspect of the system is that it is being provided under a 10-year management contract. As technologies such as storage continually advance the system will be reviewed and updated on an ongoing basis.
"We will be looking at technologies such as batteries, not necessarily to shift the generation from day to night but to improve the efficiency," Varela says.
"We don't know how the system will end up and with the evolution in technologies, we may change part or all of the power plant over the next ten years. We may also be able to extend the life of the assets beyond the ten years."
Aggreko has a history of collaboration with Gold Fields in various parts of the world. One of the most recent projects is one of the world's largest renewable energy microgrids at the Granny Smith gold mine in Western Australia.
Varela believes that Aggreko's differentiator is its ability to develop and deliver an optimum solution, drawing on the right EPC suppliers for the individual components and ensuring they are interoperable.
"They give us diesel and we give them the kilowatthours doing everything in between to meet the efficiency commitment. We have spent a lot of time making the technologies work together and developing the IT side. Other companies were interested but only committed to parts of the overall responsibility."
Sven Lunsche, Vice-President: Corporate Affairs at Gold Fields, says that the company recognised from the outset the complexity of energy delivery for the mine and that a hybrid solution would be required with solar the natural choice to meet its renewables requirements.
"The life of the mine is at least ten years and we expect further options to emerge over that time."
Varela adds that the solution is scalable both with the solar PV and the diesel gensets and that there is growing interest in such hybrid solutions, particularly for the smaller scale mining operations.
As an example of others of Aggreko's, he cites mines in Argentina that have been running on diesel with one being supplemented with storage and another with a wind farm, each the respective "best solution".
The Salares Norte mine is on track under development with operations expected to start in the last quarter of 2022, when the full thermal plant is due to come into operation.